Graves Yamaha Junior Cup R3: It's All for the Children

John Burns
by John Burns

Well, they're not really children, but they are 14 to 25 and riding R3s in MotoAmerica's new Junior Cup

Lucky us/we/I got the invite up to Buttonwillow Raceway in California to get a look at what Chuck Graves and Yamaha have in store to conquer MotoAmerica’s new Junior Cup series, which replaces last season’s KTM 390 class. KTM s are still welcome, but now they’ll be duking it out with Kawasaki Ninja 300s and 400s, Honda CBR500Rs, Suzuki GSX250Rs – and nine teenagers receiving factory-ish support from Graves Motorsports.

Chuck Graves definitely knows his way around Yamahas; the names Graves and Yamaha have been inseparable in the US for at least 20 years now, and Yamaha Race Director Keith McCarty was also on hand at Buttonwillow to welcome Yamaha’s new crop of potential stars. Day 1 was an introduction to the Graves system of racing, Day 2 would be the riders’ first time on track with their new bikes.

New toys.

Production class? Yes it is; no rare factory parts are available (and if they are, they’re not legal). However, as always, prepping a bike for a season of competition (if you want to win) does involve more than taking off the mirrors and lights. Quite a bit more in this case. Here’s everything that goes into a Graves R3.

A big part of the Graves package is learning to go about racing in a professional manner. That involves meticulous preparation and careful setup of suspension, the Suter slipper clutch, etc. – and all nine Graves R3 riders will be using interactive setup sheets to record every suspension adjustment: fork height, swingarm length, fork preload, fork clickers (all the way in is 0, first click out is 1), rear ride height, shock preload and damping adjusters, gearing… Make sure you write it all down!

The Öhlins shock has adjustments for ride height and spring preload. Mark where you started so you can get back to baseline… There’s a torque sheet in the book, says Chuck, use it!

You don’t have to change the clutch plates every race weekend, but Chuck would. Slipper clutches do wear them out faster. The R3’s design requires that you drain the coolant to get to the clutch. Follow the manual for bleeding it after you refill it. Check the oil. These engines, Chuck tells us, have run 7000 miles in endurance events without problems. Keep an eye on valve clearances, perform leakdown tests to ensure all is snug, you should be fine. If not, we have six engine crates that UPS can ship anywhere in three days…

The DID 415 drive chain looks like a gold necklace and consumes very little power; it should be replaced at 500 km. Be sure it’s properly tensioned and you shouldn’t have any issues. If you want to have somebody else work on your suspension, engine or ECU, feel free (FTECU handles the programming). But, well, the basic gist is, don’t come crying to Chuck if you wind up maladjusted. “We need to know where suspension starts and where it ends up. We don’t want to tune or advise you if you have other people work on your suspension.”

Here’s the Graves baseline and no doubt not a bad set of specs to crib from if you’re building your own R3 at home):

Graves Yamaha R3 Specifications

Engine Type321cc liquid-cooled, DOHC inline twin-cylinder; 8 valves
Bore x Stroke68.0mm x 44.1mm
Compression Ratio11.4:1
Fuel DeliveryFuel Injection, FTECU Software with Graves Map
IgnitionTransistor Controlled Ignition with FTECU software
Speed ShifterHM Moto America Spec RPM Limiter / Speed Shifter
Transmission6-speed; multiplate clutch
Final Drive415 Drive Chain from DID with Vortex Special Sprockets
ClutchSuter Slipper Clutch
Suspension / FrontGraves Modified 41mm KYB telescopic fork; w/ Öhlins FKS203 inserts
Suspension / RearGraves Modified Öhlins YA 467 Shock
Brakes / Front298mm hydraulic disc
Brakes / Rear220mm hydraulic disc
Tires / Front110/70 ZR17 Dunlop Q3+
Tires / Rear150/60 ZR17 Dunlop Q3+
L x W x H82.3 in x 28.3 in x 44.7 in
Seat Height31.7 (OEM 30.7 in)
Wheelbase1399.8 mm / 55.1102 in
Trail105.2 mm / 4.14173 in
Max. Ground Clearance6.3 in
Fuel Capacity OEM3.7 gal
Fuel Economy OEM56 mpg
Wet 10 Liters Fuel316 (OEM 368 lb / 375 lb ABS model)

2018 Graves Yamaha R3 DATA

Power HP42
Torque FT LBS21
Trail [mm]105.2 mm / 4.14173 in
Offset [mm]35mm
Wheelbase [mm]1399.2. mm / 55.0866 in
Pivot height [mm]432.7 mm / 17.0354 in
Swing ang [deg]-12.2deg
COG (x;y) [mm]676;677
Swing length [mm]582.2
Shock length [mm]287
Link ratio2.857
Fork length775
Front tire radius [mm]295
Rear tire radius [mm]309.5
Shock spring rate [N/mm]170
Shock spring preload [mm]10
Fork spring rate [N/mm]7
Fork spring preload [mm]7
Front sprocket teeth18
Rear sprocket teeth56
Squat angle [deg]31.5
Load transfer angle [deg]25.82

Forty-two rear-wheel horsies compares favorably to the 35 MO got on our last R3 dyno pull. Will it be enough to run with modified KTMs? How are we going to ensure parity between all the bikes in the series, including the new Ninja 400 that’s also eligible? That’s the job of the Junior Cup-mandated HM Shifter Kit/ Rev Limiter. For now, the R3 and Ninja twin-cylinders are allowed to rev to 13,000 rpm, the RC390 single to 10,500. The Ninja 400 twin’s limit is yet to be determined – and all those numbers can be adjusted by MotoAmerica throughout the season to try to keep things even by simply plugging a computer into the HM unit.

As Close To Dead-Even Racing As Possible
MotoAmerica Junior Cup Announces Class Rules

Now it’s time to tune the rider. Another part of the Graves package is access to multi-time AMA Champ Josh Hayes, who says he’d prefer to be racing but is also excited about his new role as “Yamaha Factory Racing Ambassador and bLU cRU Rider Coach.” When Josh got his first ride as a guest on a WERA National bike, he shared with the kids, the crew chief told him this motorcycle may not be perfect, but it’s as close to perfect as we can get it this weekend. The goal is to have a motorcycle that doesn’t cause the rider to have to work around any issues. The goal is to have a bike that doesn’t hold the rider back in any way.

It’s a 2.5-mile walk around Buttonwillow Raceway, Josh Hayes and I both made it without assistance.

That’s what Graves is going for here. In a class where all the equipment should be equal, speed will be rider-dependent. Some riders will prove to be more equal than others. If you’ve ever raced at all, you know how many times you could’ve done better if something on your bike hadn’t (insert mechanical problem here). And if something does go wrong, the Graves 18-wheeler, packed with parts, will be easy to spot in the pits at every MotoAmerica round. (Cash is the preferred exchange medium.)

How do you improve the rider? Instead of having to pull into the pits and look at lap times, each bike gets a new AIM Solo2 onboard GPS monitor (just below the speedo here) with a bar graph on the left that lights up green when we’re going faster than the last lap, red when we’re not – and records all kinds of data that can be downloaded and looked at after the session.

I wasn’t able to hang around for Day 2, but the kids had their first chance on their new motorcycles; #24 is Joseph Blasius (Nicky Hayden AMA Road Race Horizon Award Winner).

Next on the agenda is the big Dunlop tire test/shakedown cruise at Barber Motorsports Park in Alabama, March 26 and 27. After that, the MotoAmerica lights go green at Road Atlanta April 13. May the best young man win.

John Burns
John Burns

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Join the conversation
  • Jeff benson Jeff benson on Feb 10, 2018

    It'll certainly be more fun to watch than Superbike

  • Barry_Allen Barry_Allen on Feb 10, 2018

    "…a bar graph on the left that lights up green when we’re going faster than the last lap, red when we’re not…"
    OMG they just made a video game out of going fast!
    Where do I put money down on the 14 year olds?